Aircraft and hybrid with magnetic airfoil suspension and drive

ABSTRACT

An aircraft ( 10 ) is disclosed that comprises a fuselage ( 12 ) with first and second wings ( 14 ) non-rotatably secured to and extending from sides of the fuselage ( 12 ). Inner and outer tracks are secured to and encircle the fuselage ( 12 ), and airfoils ( 20 ) are operably secured between the inner and outer tracks. Means are provided for rotating the airfoils ( 20 ). The means for rotating the airfoils may be comprised of first and second drive coils ( 40 ), and first and second alternators ( 80 ) may be operably coupled to the first and second drive coils ( 40 ), respectively, to provide redundant power supplies. Permanent magnets ( 44 ) in the rotor hub may be arranged in a Halbach array or may be arranged to provide a series of alternating, opposite magnetic poles. Separate drive and suspension coils ( 38 ) may be provided in the stator ( 16 ). The concept may find further application in a lift fan or tail section of conventional aircraft. In that regard, a lift fan or tail section may be provided in which a stator magnetically levitates a lift fan rotor or tail rotor. The stator may include suspension coils ( 38 ) and drive coils ( 40 ) to eliminate the need for a drive shaft and gears to power the lift fan rotor or tail rotor.

[0001] This application is a continuation-in-part of U.S. ProvisionalPatent Application No. 60/204,182, filed on May 15, 2000.

BACKGROUND OF THE INVENTION

[0002] This invention relates to aircraft, and more particularly, to arotorcraft hybrid that incorporates a magnetic or electromagneticvertical takeoff and landing (“VTOL”) system or an aircraft that uses amagnetic suspension and drive for a tail rotor or lift fan. Conventionalhelicopters or rotorcraft are versatile aircraft that allow for verticaltakeoff and landing and that offer reasonable amounts of vertical liftand horizontal speed up to the retreating blade limit. The basichelicopter configuration is the result of mechanical evolution thatapplied the present state of the art over many years. While theconventional rotorcraft offers many advantages, it still suffers from anumber of disadvantages. For example, rotor blades are long but providemeaningful lift over only a relatively short segment at the ends of therotor blades. This means that the center of the rotor area is not beingeffectively utilized. Also, because the hub about which the rotor bladesrotate is relatively small, only a small number of airfoils may be used.Similarly, because the rotor shaft is relatively small, the weight ofthe craft and any load carried may place significant stress on theshaft. These disadvantages severely restrict the lift capabilities ofrotorcraft. Further, having the center of gravity displacedsubstantially below the center of lift leads to a relatively unstableconfiguration. Further still, the horizontal speed of conventionalrotorcraft is undesirably limited by the retreating blade limit. Also, atail rotor is needed for stability, and tail rotors of conventionalhelicopters suffer from a number of problems. For example, mechanicallinkages, such as drive shafts and gears, that mechanically couple tailrotors to main engines add unnecessarily to the weight of helicoptersand can cause mechanical and reliability problems.

[0003] Conventional fixed wing aircraft are versatile as well and offermany advantages. Aerodynamic advantages allow fixed wing aircraft totravel at greater speeds and carry heavier payloads. Still, conventionalfixed wing aircraft typically lack VTOL capabilities. Hybrid aircraftsuch as the Harrier, Osprey, and Joint Strike Fighter have beendeveloped in an attempt to offer a fixed wing aircraft having VTOLcapabilities or very short takeoff and landing (“VSTOL”) capabilities.While these are remarkable aircraft, they too suffer from a number ofshortcomings. For example, the vertical lift capabilities of theseaircraft is quite limited and do not approach the vertical liftcapabilities offered by many conventional helicopters, so they are poorcandidates for transporting heavy payloads. Also, these aircraft arerelatively unstable during VTOL or VSTOL maneuvering. Further still,mechanical linkages, such as drive shafts and gears, that mechanicallycouple lift fans and turbine engines can add unnecessarily to the weightof aircraft such as the Joint Strike Fighter and can lead to mechanicaland reliability problems.

SUMMARY OF THE INVENTION

[0004] It is therefore an object of the present invention to provide arotorcraft or rotorcraft hybrid that combines the VTOL capabilities of arotorcraft with the speed of a fixed wing aircraft.

[0005] It is a further object of the present invention to provide acraft of the above type that offers superior lift capabilities.

[0006] It is a further object of the present invention to provide acraft of the above type that offers horizontal speed that is not limitedby the speed of the retreating blade.

[0007] It is a further object of the present invention to provide acraft of the above type that offers superior stability during takeoff,landing, and cruising.

[0008] It is a further object of the present invention to provide acraft of the above type in which a majority of the airfoil length isused to provide lift.

[0009] It is a further object of the present invention to provide acraft of the above type in which the center of mass of the craft islocated at or near the center of lift.

[0010] It is a further object of the present invention to provide acraft of the above type that offers aerodynamic shrouding of theairfoils.

[0011] It is a further object of the present invention to provide acraft of the above type that offers stealthy shrouding of the airfoils.

[0012] It is a further object of the present invention to provide acraft of the above type that uses electromagnetic means to suspend anddrive the airfoils.

[0013] It is a further object of the present invention to provide acraft of the above type that provides strong, light rotor and statorhubs that allow for consistent drive and suspension despite some radialexpansion of the rotor hub during operation.

[0014] It is a further object of the present invention to provide acraft of the above type that uses an increased number of airfoils foradded lift capabilities.

[0015] It is a further object of the present invention to provide acraft of the above type that uses two sets of counter-rotating airfoilsfor increased stability without the need for a tail rotor.

[0016] It is a further object of the present invention to provide acraft of the above type that provides for safe continued suspension anddriving of the airfoils in the event of a partial power failure.

[0017] It is a still further object of the present invention to providea craft of the above type that provides for continued suspension androtation of the airfoils even in the event of a total power failure.

[0018] It is a still further object of the present invention to providea craft of the above type that incorporates a tail rotor or lift fan ofa type that eliminates the need for a drive shaft and gears.

[0019] It is a still further object of the present invention to providea craft of the above type that incorporates a tail rotor or lift fan inwhich a rotor is magnetically levitated and driven by a stator.

[0020] Toward the fulfillment of these and other objects and advantages,the aircraft of the present invention comprises a fuselage with firstand second wings non-rotatably secured to and extending from sides ofthe fuselage. Inner and outer tracks are secured to and encircle thefuselage, and airfoils are operably secured between the inner and outertracks. Means are provided for rotating the airfoils. The means forrotating the airfoils may be comprised of first and second drive coils,and first and second alternators may be operably coupled to the firstand second drive coils, respectively, to provide redundant powersupplies. Permanent magnets in the rotor hub may be arranged in aHalbach array or may be arranged to provide a series of alternating,opposite magnetic poles. Separate drive and suspension coils may beprovided in the stator. The concept may find further application in alift fan or tail section of conventional aircraft. In that regard, alift fan or tail section may be provided in which a stator magneticallylevitates a lift fan rotor or tail rotor. The stator may includesuspension coils and drive coils to eliminate the need for a drive shaftand gears to power the lift fan rotor or tail rotor.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above brief description, as well as further objects, featuresand advantages of the present invention will be more fully appreciatedby reference to the following detailed description of the presentlypreferred but nonetheless illustrative embodiments in accordance withthe present invention when taken in conjunction with the accompanyingdrawings, wherein:

[0022]FIG. 1 is an overhead view of an aircraft of the presentinvention;

[0023]FIG. 2 is a rear view of an alternate embodiment of an aircraft ofthe present invention;

[0024] FIGS. 3-5 are schematic, side elevation views of alternateembodiments of an aircraft of the present invention;

[0025] FIGS. 6-8 are sectional, side elevation views of alternateembodiments of an aircraft of the present invention;

[0026]FIG. 9 is a schematic representation of a Halbach array ofpermanent magnets;

[0027]FIG. 10 is a sectional view of taken along line 10-10 or FIG. 7,showing an internal rotor hub and stator support coils;

[0028]FIG. 11 is a sectional, side elevation view of an internal rotorhub and stator;

[0029]FIG. 12 is a sectional view taken along line 12-12 of FIG. 11;

[0030]FIGS. 13 and 14 are graphical representations of total lift of aconventional helicopter and an aircraft of the present invention,respectively;

[0031]FIG. 15 is a sectional view of an alternator for use in practicingthe present invention;

[0032]FIG. 16 is a sectional view of a variable bypass engine includingan alternator;

[0033]FIGS. 17 and 18 are schematic alternate embodiments showingalternators coupled with drive coils of upper and lower electric motors;

[0034]FIG. 19 is a schematic view of magnetic field paths when only asingle alternator is active;

[0035] FIGS. 20-22 are diagrams of a power delivery system of thepresent invention;

[0036]FIG. 23 is a schematic view of a conventional tail rotor or liftfan rotor;

[0037]FIG. 24 is a schematic view of a tail rotor or lift fan rotor ofthe present invention;

[0038]FIG. 25 is a schematic view of downwash and turbulence encounteredduring VTOL operation of an Osprey aircraft; and

[0039]FIG. 26 is a schematic view of downwash and turbulence encounteredduring VTOL operation of an aircraft of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0040] Referring to FIG. 1, the reference numeral 10 refers in generalto an aircraft of the present invention. The aircraft has a fuselage 12,wings 14, inner and outer tracks or stators 16 and 18 encircling thefuselage, and airfoils 20 extending between the tracks 16 and 18. Meansare provided for rotating the airfoils 20. Engines 22, such as turbineengines, may be provided.

[0041] As illustrated in FIGS. 1-4, the fuselage 12 and wings 14 maytake any number of shapes, sizes and configurations. Also, engines 22may be affixed to the fuselage 12 or to the wings 14. Referring to FIG.2, a cargo area 24 may form part of or be disposed below the fuselage12. As shown in FIG. 3, in one alternate embodiment, the airfoils may bedisposed below the fuselage 12 similar to a hovercraft. Although notclear from the schematic representation in FIG. 3, the top surface ofthe wing is shuttered for horizontal flight. As seen in FIG. 4, weapons26, such as a large caliber gun, may be incorporated into the aircraft,and the aircraft may also include armor 28. As also seen in FIG. 4, theaircraft need not have wings 14 but may instead be used with or withouta fairing 30. As best seen in FIG. 5, when an engine 22 is affixed tothe fuselage 12, the engine may be disposed between upper and lower setsof airfoils, and an inlet air path 32 and outlet thrust path 34 may beprovided for the engine 22 to receive inlet air and to provide thrustbetween the upper and lower sets of airfoils 20. Because the airfoils 20are not disposed above the fuselage 12 as in a conventional helicopter,a safety ejection seat may be used in an aircraft of the presentinvention 10.

[0042] As illustrated in FIGS. 6-8, the rotor hubs 36, and thereforeairfoils 20, are magnetically levitated and driven about stators 16. Arotor hub 36, stator hub 16, and associated support coils 38 and drivecoils 40 form a large diameter, distributed, electric motor. Each set ofairfoils 20, rotor hubs 36, and stators 16 are substantially identical,so only one of each will be described in detail. As best seen in FIG. 1,the stator hub 16 encircles the fuselage 12 to form a large diameter,circular, inner track 16. The stator hub 16 and rotor hub 36 may beshaped or configured in any number of ways for operably coupling thestator hub 16 and rotor hub 36. As seen in FIG. 6, the rotor hub 36 maybe in the shape of an external hub that mates with a protruding portionof the track or stator 16. In this embodiment, the protruding portion ofthe stator 16 is comprised of an alternating series of support coils 38and drive coils 40. The external rotor hub 36 is comprised of alightweight metal with carbon fiber bands 42 embedded therein forfurther weight reduction.

[0043] In the external rotor hub 36 embodiment depicted in FIGS. 6 and8, three sets of permanent magnets 44 disposed in Halbach arrays arealso disposed in the rotor hub 36 for interaction with the support 38and drive coils 40 in the stator 16. As best seen in FIG. 9, a Halbacharray is an arrangement of permanent magnets 44 that results in aperiodic, permanent magnetic field on one side 46 and only a smallmagnetic field 48 on the other side, as illustrated in FIG. 9. FIG. 9shows a Halbach array of permanent magnets 44 and its interaction with aseries of conducting levitation and drive coils 40. Arrows 50 show theorientations of the polarities of the magnets 44, arrows 48 show how themagnetic fields cancel, and arrows 46 show how the magnetic fieldscombine. Moving the Halbach array past a series of conducting loopsinduces current in the loops, producing a magnetic field that opposesthe magnet movement and that generates a repulsive force. Electric driveof the Halbach array is accomplished by interspersing current driven,conducting loops regularly between support or suspension loops 38 thatgenerate a moving magnetic field that pulls or pushes the Halbach arrayalong the conducting loop structure. This is similar to the Inductrak™magnetically levitated train system developed at Lawrence LivermoreNational Laboratory.

[0044] As best seen in FIGS. 7 and 11, airfoil supports 52 are securedto the rotor hub 36. As seen in FIG. 8, controlling the pitch of thecounter rotating airfoils is also accomplished using magnetic bearings,such as Halbach bearings 54. The pitch of each airfoil 20 is controlledvia a pitch control arm 56 that is connected to a skate that rides in acylindrical magnetic bearing ring. The distance from the rotor hub 36 tothe bearing ring is controlled with actuators 58 so that the ringcontrols the pitch of each airfoil 20. The pitch control system issimilar to a swash plate in a conventional rotorcraft system.

[0045] In the preferred embodiment, the rotor hub 36 is an internalrotor hub such as shown in FIG. 7. In this embodiment, a channel 60 isformed in the stator 16, and a flange portion of the internal rotor hub36 fits within the channel 60. Sets of support coils 38 are disposedabove and below the channel 60, and a set of drive coils 40 is disposedat an inner portion of the channel 60. Although not preferred, it isunderstood that drive coils 40 may be interspersed between support coils38 above and below the channel 60. The rotor hub 36 is comprised of alightweight metal with carbon fiber bands 42 embedded therein forfurther weight reduction. An airfoil support 52 is secured to the rotorhub 36. As seen in FIGS. 7 and 10, a series of permanent magnets 44arranged with alternating poles is disposed in a flange area of therotor hub 36. As best seen in FIG. 7, the permanent magnets 44 arecovered with a thin conductor shield 62 to prevent the drive fields fromreaching the magnets 44 and changing their magnetization. Covering thepermanent magnets 44 with a thin conducting shield 62 to preventcross-magnetization is an important feature. Although this feature maynot be clearly shown in each drawing, it is understood that otherpermanent magnets 44 found in the rotors 36 will also use a similar thinconducting shield 62. This conducting covering of the magnets 44 in theflange area also serves to center the rotor hub 36 with respect to thestator 16 because the conducting surface interacts with the magneticfields in the support coils 38. The internal rotor hub 36 configurationis shown in more detail in FIG. 11. As seen in FIG. 11, the top andbottom support coils 38 are held in place by top, center, and bottomclamps 64, secured in place with bolts 66. FIG. 12 shows the clamps 64holding the support coils 38 in place, with the internal rotor hub 36disposed between the upper and lower support coils 38. Although notdepicted, corresponding support coils 38 positioned above and below thestator 16 may be connected in series to provide a “null flux”configuration as described in more detail below.

[0046] Table 1 sets forth sample, hypothetical parameters for two,representative embodiments of the present invention, representingversions for light and heavy duty. TABLE 1 Hypothetical Parameters ofLight and Heavy Duty Aircraft Parameters Light Heavy Rotor HubParameters Rotor Hub diameter 5 m 10 m Rotor Hub circumference 15.7 m37.68 m Number of sectors 12 28 Number of airfoils/sector 1 1 Lift andDrag per Airfoil Airfoil length 1.2 m 2 m Airfoil chord 0.5 m 0.5 m Airdensity 1.29 kG/m³ 1.29 kG/m³ Lift coefficient 0.8 0.8 Drag coefficient0.05 0.05 Avg airfoil velocity 100 m/s 100 m/s Airfoil area 0.6 m² 1 m²Lift/airfoil = 3096 Nt 5160 Nt 0.5*D*Af*Cl*Vt² Drag/airfoil = 193.5 Nt322.5 Nt 0.5*D*Af*Cd*Vt² Number of airfoils/rotor hub 12 28 Number ofrotor hubs 2 2 Total lift 74,304 Nt 288,960 Nt Total lift 7,582.0 kg29,485.7 kg Total lift 16,680.5 lbs 64,868.6 lbs Total lift 8.3 Tons32.4 Tons Total airfoil drag 2,322.0 Nt 9,030.0 Nt Total airfoil drive232,200.0 Watts 903,000.0 Watts power required Total airfoil drive 311.3Hp 1210.5 Hp power required

[0047] As illustrated by Table 1, the large diameter hub of the presentinvention allows the use of a larger number of rotor blades or airfoils20 in a more efficient manner than conventional rotorcraft. This is alsoseen in FIGS. 13 and 14, which compare total lift of a conventionalhelicopter 67 to the total lift of an aircraft of the present invention10. The areas 68 under the curves in FIGS. 13 and 14 represent the totallift of each rotorcraft or aircraft as a function of rotor blade 70 orairfoil 20 length. As illustrated by FIG. 13, because lift isproportional to the blade velocity squared, conventional helicopterrotor blades or airfoils 70 provide meaningful lift over only arelatively short segment at the ends of the rotor blades 70. FIG. 14shows that comparable or superior results may be obtained using moreairfoils 20 having shorter lengths rotating about a larger diameter.

[0048] Referring again to FIG. 6, the aircraft preferably has two setsof counter-rotating airfoils 20. A fairing 30 is preferablynon-rotatably secured to the fuselage 12 by a support structure 72disposed between the upper and lower sets of airfoils 20. A magneticbearing 74 is provided on an inner portion of the fairing 30 to providean outer track 18 to further guide the airfoils 20. The outer track 18may be formed in any number of ways, quite similar to the inner track 16described above. For example, a stator may be secured to the fairing 30,and the stator may mate with an internal or external rotor hub. Becausethe forces and lift requirements at the outer track 18 will typically beless extreme than at the inner track 16, and because there should be noneed for drive means in the outer track 18, the construction of theouter track 18 may be greatly simplified. For example, the stator maysimply have permanent magnets 44 disposed along upper and lower surfacesof a channel 60, and the ring hub rotor may be a simple metal hub, or ametal hub with embedded carbon fiber bands 42. Similar to the innertrack 16, Halbach arrays of permanent magnets 44 may be used at theouter track 18 as well.

[0049] The fairing 30 may be aerodynamically shaped to act as an airfoilduring forward movement and may be shaped to improve the stealthconfiguration of the aircraft. Shutters 76 may be provided to furtherimprove the aerodynamic and stealth capabilities of the aircraft.Directional flaps 78 (FIG. 5) may also be used for improved low speeddirectional maneuvering and hovering. As illustrated by FIGS. 1 and 2,rather than employing a simple, circular, airfoil shaped fairing 30, thefairing 30 may take the shape of a more traditional fixed wing structurethat may be non-rotatably secured to the fuselage 12 by the supportstructure 72. This would enable an aircraft of the present invention toprovide hybrid characteristics similar to the Harrier, the Joint StrikeFighter, or the Osprey. As seen in FIGS. 1 and 2, the turbine engines 22may be affixed to the fuselage 12, inside the circumference of the innertracks 16, or may be affixed to the wings 14, outside the circumferenceof the outer tracks 18. As best seen in FIGS. 1 and 5, when the turbineengines 22 are affixed to the fuselage 12, the separation of the upperand lower sets of airfoils 20 allows the use of airflow inlets 32 andjet thrust apertures 34 that pass between the upper and lower sets ofairfoils 20 and upper and lower inner and outer tracks 16 and 18.

[0050] The requirements for an alternator 80 needed to drive theelectromagnetic hubs of the present invention are challenging butobtainable. The alternator 80 must be compatible with jet enginerotational speeds and temperatures, controllable, lightweight, andcapable of generating large amounts of electrical power. As seen in FIG.15, a permanent magnet alternator 80 such as one developed at LawrenceLivermore National Laboratories, may be used to convert engine torque toelectrical energy for powering the electromagnetic drive of the presentinvention and may be used for flywheel energy storage. This alternator80 is capable of providing a specific power density of approximately 30kW/kG. Because of its small diameter and simple, rugged construction,this alternator 80 is able to rotate at speeds of around 30,000 rpmwithout being torn apart by centrifugal forces. The alternator 80 issimilar to a standard induction motor that is “turned inside out.” Inthat regard, the stator 82 is on the inside, and the rotor 84 is on theoutside. The stator 82 is coupled via shaft 86 to the turbine drive of ajet turbine engine 22 to provide the engine torque. A Halbach array ofpermanent magnets 88 is secured about the circumference of an innerportion of the rotor 84. Magnetic bearings 90 and a generator outputwinding 92 are secured to the stator 82. Electrical output passesthrough conductor 94. Although the alternator 80 may be a single-phasealternator, the alternator is preferably a multi-phase alternator and ismore preferably a three-phase alternator.

[0051] As seen in FIG. 16, the alternator 80 receives engine torque fromand is located near the inlet of a jet turbine engine 22. The airflow atthe inlet to the engine 22 cools the alternator 80, particularly thepermanent magnets and alternator windings. The engine 22 is preferably avariable bypass engine that is capable of delivering varying amounts ofpower to the alternator 80 depending upon the needs of the system. Flapsor diverters 96 are operable to provide a variable inlet geometry.Referring to FIG. 17, the top and bottom electric motors are dividedinto multiple sections corresponding to one or more groupings of drivecoils 40.

[0052] As described in more detail below, for purposes of redundancy,the drive coils 40 in the unshaded sections of upper and lower electricmotors are driven by alternator “A”, and the drive coils 40 in theshaded sections of the upper and lower electric motors are driven byalternator “B”. As also illustrated in FIG. 18, any number of engines 22and alternators 80 may be used to drive the drive coils 40 in upper andlower electric motors. For reasons to be described, as seen in FIG. 19,magnetic field bridge paths 98 can be provided to magnetically couplecorresponding sections of the upper and lower electric motors.

[0053]FIG. 20 depicts one embodiment of a system for energizing a drivecoil 40 of the present invention. Alternator 80 provides high frequencycurrent to alternator buss 100.

[0054] Alternator buss 100 is electrically coupled with capacitor 102,and controlled rectifiers or CRs, CR-A 104 and CR-B 106, act aselectronically controlled gates between the alternator buss 100 andcapacitor 102. Capacitor 102 supplies lower frequency current to drivecoil, with controlled rectifiers CR-C 108 and CR-D 110 acting aselectronically controlled gates between the capacitor 102 and drivecoil. As seen in FIGS. 21 and 22, drive coils 40 may be interspersedbetween support coils 38. As also seen in FIG. 22, each drive coil 40has an associated sensor 112 that determines the polarity and positionof the rotor 36 and that therefore determines when to initiate currentflow to the drive coil 40. The distribution of drive coils 40 in betweensupport coils 38 seen in FIG. 22 is similar to the distribution of drivecoils in the Lawrence Livermore National Laboratory Inductrak™ system.Although not clear from FIG. 22, the drive coils 40 above the rotor 36and below the rotor 36 are connected and driven in series to make themotor thrust symmetrical. In the preferred embodiment, such as seen inFIG. 7, planes of the support and drive coils 38 and 40 areperpendicular to minimize cross coupling. In an alternate embodiment,the support and drive system of the present invention may also be usedto overcome problems experienced with conventional tail rotors or liftfans 114. A helicopter typically has a main rotor that rotates about afirst axis and a tail rotor 116 that rotates about a different axis thatis substantially perpendicular to the first axis. Similarly, in anaircraft that uses a combination of a jet turbine engine 22 and a liftfan, the turbine typically rotates about a first axis and the lift fanrotor 116 typically rotates about a different axis that is substantiallyperpendicular to the first axis. As seen in FIG. 23, conventional tailrotors and lift fans 114 have drive shafts 118 and transmissions orgears 120 that mechanically couple the rotor 116 to an engine 22. Thesedrive shafts 118 and gears 120 are highly stressed, add undesirably tothe weight of the craft, and suffer from reliability problems. Thepresent invention eliminates the need for a drive shaft 118 andtransmission 120 by using a distributed electric motor to suspend anddrive the rotor 116. As seen in FIG. 24, a series of permanent magnets44 may be provided in the tip ends of the rotor 116. A stator 16 mayencircle the rotor 116, and the stator 16 may be provided with supportand drive coils 38 and 40 that encircle the circumference of the rotor116. The high efficiency electric motor drive and magnetic suspension isdistributed around the circumference of the fan or rotor 116. Note thatseveral fans can be driven in series in this manner if additional thrustis needed. In this manner, the rotor 116 need not be mechanicallycoupled to a drive shaft 118 or gear 120. It is simpler and morereliable to provide power to the tail rotor or lift fan rotor 116 in theform of electrical energy produced by a very compact alternator ratherin the form of torque. Using a tail rotor or lift fan of the presentinvention reduces stress on the mechanical components, allows for theelimination of some problematic components, allows for higherredundancy, allows for the elimination of some single point failuremodes, and improves performance of the tail rotor or lift fan.

[0055] In operation of an aircraft such as one depicted in FIGS. 1-4, anoperator would activate the turbine engines 22 to provide power to thealternators 80. Each alternator 80 converts engine torque to electricalenergy and provides current to their portions of the upper and lowerdistributed electric motors. Because the electric motors are dividedinto sections, a single engine 22 and alternator 80 may power drivecoils 40 in both the upper and lower electric motors in the event one ormore engines 22 or alternators 80 fails. It is also important to pointout that this system provides for redundancy without the need forover-designed and heavy transmissions and cross shafts that aretypically necessary in conventional multi-engine transports andtilt-rotor systems to provide redundancy.

[0056] When the electric motors are initiated, the rotors 36 andassociated airfoil sections are at rest, resting on integral wheels orrollers. The drive coils 40 are activated to produce moving magneticfields that engage and push or pull the permanent magnets 44 in therotor 36 to induce rotation of the rotor 36. Rotation of the rotor 36 isincreased in a synchronous manner. Magnetic levitation of the rotor 36is provided by the movement of the permanent magnets 44 embedded in therotor 36 past the shorted, suspension or support coils 38. Referring toFIG. 22, the movement of the permanent magnets 44 in the rotor 36induces currents in the support coils 38 that produce a magnetic fieldthat repels the rotor 36 magnetic field. This arrangement provides animportant safety feature. Since the magnetic levitation or support coils38 are not powered, even a complete power failure will not immediatelystop the magnetic levitation. Instead, the magnetic levitation will bepresent as long as the rotors 36, and therefore airfoils 20, are moving.This enables an operator to use auto-rotation techniques in the event ofa failure of all power systems. As discussed above in connection withFIG. 19, magnetic field bridges can be used to operably connect theupper and lower stators 16 to create low reluctance or shunt flux pathsbetween them. In normal operation, the moving magnetic fields move in acontinuous fashion about the circumference of either the top electricmotor or the bottom electric motor. In the event of a partial failure,the moving magnetic fields 122 that were continuous about thecircumference of a motor can remain continuous by traversing a lowreluctance path from the top motor to the bottom motor and by traversinganother low reluctance path from the bottom motor to the top motor.

[0057] As mentioned above, the support coils 38 may also be disposed ina “null flux” configuration (not shown) by connecting correspondingpairs of support coils 38 above and below a rotor 36 in series. In thisnull flux configuration, the net voltage induced in the coils due to thepermanent magnets 44 in the rotor 36 moving past the coils is zero whenthe rotor 36 is vertically centered in between the support coils 38.This approach is commonly used in the magnetic levitation of trains andhas the advantage of minimizing the circulating currents and thusreducing the power dissipated in the coils when the rotor 36 iscentered. When the rotor 36 deviates from the central symmetricalposition, the induced currents rapidly increase to produce thelevitating magnetic field.

[0058] A variable frequency current is provided to the drive coils 40 toprovide for different rotational speeds by the rotor 36. In theconfigurations depicted FIGS. 20-22 for producing the variable frequencycurrent through the drive coils 40, the high frequency alternator buss100 is used to charge the central capacitor 102. Referring to FIG. 20,the CRs are electronically controlled gates that permit current to flowonly in the direction of the arrows.

[0059] CR-B 106 is closed until the capacitor 102 is charged to apositive voltage. After CR-B 106 is deactivated at an alternator 80current zero and the associated sensor 112 (FIG. 22) determines themagnetic field of the rotor 36 is in the correct position, CR-D 110 isclosed to produce a positive half cycle sinusoid in the drive coil andreverse the voltage on the central capacitor 102. The half cycle currentproduces a magnetic field that repels the rotor 36 magnetic field tomove the rotor forward. During the initial half cycle current, thecontrol voltage is removed from CR-D 110 which then ceases conductionwhen the current returns to zero. When the sensor 112 determines thatthe rotor 36 has moved to present the opposite polarity of magneticfield, CR-C 108 is closed to generate the negative half cycle and returnthe capacitor 102 voltage to a positive polarity. As the rotor 36 speedincreases, the delay between the positive and negative half cycles ofcurrent in the drive coil is reduced such that the delay is zero atmaximum rotor 36 speed. Note that CR-A 104 and CR-B 106 can becontrolled to add electrical energy to the central capacitor 102 whenthe capacitor 102 voltage is negative or positive to replace the energylost in moving the rotor 36.

[0060] The drive coils 40 may be connected in series or parallelcombinations or may even be operated individually to provide the maximumredundancy and to match the impedance of the alternators. If drive coils40 are provided above and below the rotor 36, the drive coils 40 aredriven in series to make the motor thrust symmetrical. Any number ofconfigurations may be employed to provide the driving force to rotatethe rotor 36 relative to the stator 16, including configurations that donot use capacitors, in which case, the system is designed to deliveronly the energy required to drive the rotor 36 and to replace the energydissipated in the coil resistance while storing minimum energy. Thepower delivery system of the present invention is extremely redundantand reliable due to the distributed drive locations, the common powerbuss, and multiple power sources. Note also that the azimuthalorientation of the craft is dependent upon the net torque differentialin the top and bottom electric motors.

[0061] Accordingly, precisely controlling the number of drive sectionsthat are actuated can be used to orient the craft precisely to anydirection of travel. Using the internal rotor hub 36 configuration asdepicted in FIG. 7 simplifies the construction and operation of theelectric motors. For example, it eliminates the need to use a Halbacharray of permanent magnets. It also permits the rotor hub 36 to expandradially as its speed increases without loss of magnetic interaction andrepulsion.

[0062] One advantage of an aircraft of the present invention 10 over aconventional helicopter is the possibility of higher lift capability fora given diameter system. One important aspect of the present inventionis that it can be operated in hover mode by reducing the blade attackangle, thereby generated the same downwash as a conventional helicopter.Another important aspect of the present invention is that, by increasingthe pitch angle, an aircraft of the present invention 10 will offerhigher climb rates, higher load capabilities, and more versatility. Anaircraft of the present invention also differs from a conventionalhelicopter in that it offers more options for forward propulsion. Ofcourse, the airfoils 20 used for VTOL operations may also be used forhorizontal flight by tilting the rotor 36 plane to provide a portion ofthe downward thrust vector in the forward or rearward direction, verysimilar to horizontal propulsion of a conventional helicopter. Low speedhorizontal maneuvering may also be accomplished using directional flapsor slats 78 that direct the downward airflow rearward, forward, or tothe side (FIG. 5). This method of maneuvering is capable because of thepresence of a body or fuselage 12 at the inner circumference of therotor hub 36 and the presence of a fairing 30 encircling the outercircumference of the airfoils 20. Accordingly, this mode of operation isnot possible in conventional helicopters or in tilt-rotor systems. Highspeed transport is also possible, such as by using a variable bypass jetturbine engine 22 (FIG. 16) that also powers the alternator 80. DuringVTOL operations, flaps 96 are closed to provide the maximum power to thealternator 80 and to minimize the thrust fan load. During the transitionto horizontal flight, flaps 96 are opened to transfer power to thethrust fans 124. As the load on the alternator 80 is decreased, the flowthrough the fan is increased to transfer the power flow to the fan toobtain maximum forward thrust The directional flaps or slats 78 (FIG. 5)may also be used to divert the downwash 126 from the airfoils 20 foradditional thrust. As the horizontal speed increases, the fairing 30 andwings 14 provide increasing portions of the lift reducing the load onthe airfoils 20, until the thrust of the turbine engines 22 is used topower horizontal flight as in a conventional jet aircraft. At thispoint, the airfoils 20 are operated at or near zero pitch.

[0063] Violent downwash 126 is a concern during VTOL and VSTOLoperations, particularly for heavy lift tilt-rotor systems 128, and thepresent system offers advantages in addressing downwash 126 concerns.Referring to FIGS. 25 and 26, during VTOL operations, the total downwash126 for two systems with the same load and same diameter are identical.

[0064]FIGS. 25 and 26 illustrate the very chaotic interaction of thedownwash 126 patterns of a multi-tilt rotor system 128 and the uniformdownwash 126 pattern of an aircraft of the present invention 10. Thetotal magnitude of the downwash 126 for both systems must be the same inorder to lift the same loads, but the aircraft of the present invention10 creates a downwash 126 that is distributed around the circumferenceof the system diameter, whereas the tilt-rotor 128 downwash 126 is muchmore locally intense and interactive. In addition, the downwash 126 froman aircraft of the present invention can be dispersed using vanes on theunderside of the aircraft to make the impact of the downwash 126 on theground less than that of the downwash from the tilt-rotor system. Anaircraft of the present invention 10 offers many advantages overconventional rotorcraft and fixed wing aircraft. The use of counterrotating sets of airfoils 20 eliminates the need for a tail rotor andprovides a very stable platform. The large diameters and circumferencesof the rotor hub 36 and stator 16 allow the use of a large number ofairfoils 20 for additional lift. The large diameters and circumferencesof the rotor hub 36 and stator 16 also make it easy to use additionalengines 22 and alternators 80, without heavy, complex, unreliablemechanical linkages, to power the electric motors for heavy dutyapplications or for redundancy. The large diameters and circumferencesof the rotor hub 36 and stator 16 also spread the aircraft and loadweight over a much larger area such that the magnetic bearingrequirements are reasonable and the total lift capacity is much largerthan that of other approaches. For example, an aircraft using a Halbacharray configuration of permanent magnets 44, such as used in FIGS. 6 and8, can generate a magnetic repulsive force that can support 40 metrictons per square meter of surface area (4 kG/cm² or 56 lb/in²) at avelocity of approximately 20 m/s. This is approximately 8 times themaximum lift generated by an airfoil of 7 lbs/in². As illustrated inTable I, above, an aircraft of the present invention 10 with a rotor hub36 diameter of approximately 10 m would be capable of providing lift ofgreater than approximately 30 tons.

[0065] In addition to the readily apparent civilian uses for the presentinvention, the heavy lift capabilities and air mobility of aircraft ofthe present invention 10 might provide several advantageous militaryapplications. For example, the heavy lift capabilities and large amountsof electrical power onboard make an aircraft of the present invention anideal platform for many heavy electric weapons, such as electromagneticguns, lasers, and particle beams. The aircraft provides air mobility,fast response and deployment, and the engines 22 and alternators 80 usedfor VTOL operations may also be employed to provide a large amount ofelectrical power to weapons systems. Further, the use of the rotatingrotor hubs 36 as flywheel energy storage enables electric weaponsapplications to be used in flight. The use of a fairing 30 and shutters76 to enshroud the airfoils 20 increases the efficiency of the airfoils,reduces audible noise, and enables stealth technologies to be betterdeployed in a rotorcraft. Further still, the aircraft is relativelyquiet, stealthy, and fast and is capable of carrying large loadsincluding armor, personnel, and weapons. The aircraft also providestransportation that is not hampered by common obstacles such as terrain,land mines, water, and rivers, and its VTOL capabilities mean that norunways or landing strips are required.

[0066] Other modifications, changes and substitutions are intended inthe foregoing, and in some instances, some features of the inventionwill be employed without a corresponding use of other features. Forexample, the aircraft may be used with or without a fairing 30. Also,The support coils 38 and drive coils 40 may be disposed and powered inany number of ways. Further, the stator 16 and rotor hub 36 may take anynumber of shapes and sizes and may be operably coupled in any number ofways. Further still, any number of ways may be used to supply power tothe electric motors, and drive coils 40 may be used to push or pull theappropriately aligned magnets 44. It is of course understood that allquantitative information is given by way of example and is not intendedto limit the scope of the present invention. Accordingly, it isappropriate that the appended claims be construed broadly and in amanner consistent with the scope of the invention.

What is claimed is:
 1. An aircraft, comprising: a fuselage; first andsecond wings non-rotatably secured to said fuselage and extending fromsides of said fuselage; a first inner track secured to and encirclingsaid fuselage; a first outer track secured to and encircling saidfuselage; a first plurality of airfoils operably secured between saidfirst inner track and said first outer track; and first means forrotating said first plurality of airfoils in a first direction.
 2. Theaircraft of claim 1, further comprising first and second engines securedto said first and second wings, respectively.
 3. The aircraft of claim1, further comprising a turbine engine secured to said fuselage.
 4. Theaircraft of claim 1, further comprising: a second inner track secured toand encircling said fuselage below said first inner track; a secondouter track secured to and encircling said fuselage below said firstouter track; a second plurality of airfoils operably secured betweensaid second inner track and said second outer track; and second meansfor rotating said second plurality of airfoils in a second direction. 5.The aircraft of claim 4 wherein said first direction is either clockwiseor counterclockwise, and said second direction is opposite said firstdirection.
 6. The aircraft of claim 4, further comprising an enginesecured to said fuselage, said engine disposed to provide thrust thatpasses between said first and second outer tracks.
 7. The aircraft ofclaim 4, wherein said first means for rotating said first plurality ofairfoils comprises a first and a second drive coil, and said secondmeans for rotating said second plurality of airfoils comprises a thirdand a fourth drive coil, and further comprising: a first alternatoroperably connected to said first drive coil and said third drive coil;and a second alternator operably connected to said second drive coil andsaid fourth drive coil.
 8. The aircraft of claim 1, further comprising:a first rotor hub, said first plurality of airfoils being secured tosaid first rotor hub; and a plurality of permanent magnets secured tosaid first rotor hub and arranged in a Halbach array.
 9. The aircraft ofclaim 8, further comprising a conductor covering said plurality ofpermanent magnets.
 10. An aircraft, comprising: a fuselage; a firststator secured to and encircling said fuselage; first and second drivecoils adjacent said first stator; a first plurality of airfoils movablycoupled with said first stator; a first alternator operably connected tosaid first drive coil; and a second alternator operably connected tosaid second drive coil.
 11. The aircraft of claim 10, furthercomprising: a second stator secured to and encircling said fuselagebelow said first stator; third and fourth drive coils adjacent saidsecond stator; a second plurality of airfoils movably coupled with saidsecond stator; said first alternator being operably connected to saidthird drive coil; and said second alternator being operably connected tosaid fourth drive coil.
 12. The aircraft of claim 11, further comprisinga plurality of magnetic field bridges operably connecting said firststator and said second stator to create a first and second shunt fluxpath between said first stator and said second stator.
 13. An aircraft,comprising: a fuselage; a first stator secured to said fuselage; a firstsuspension coil secured to said first stator; a first drive coil securedto said first stator; a first rotor hub operably coupled to said firststator; a first plurality of permanent magnets secured to said firstrotor hub and arranged in a Halbach array; and a first plurality ofairfoils secured to said first rotor hub.
 14. The aircraft of claim 13,further comprising: a fairing non-rotatably secured to said fuselage;and a first magnetic bearing secured to said fairing, distal ends ofsaid first plurality of airfoils being operably coupled with said firstmagnetic bearing.
 15. The aircraft of claim 14, further comprising: asecond stator secured to said fuselage; a second suspension coil securedto said second stator; a second drive coil secured to said secondstator; a second rotor hub operably coupled to said second stator; asecond plurality of permanent magnets secured to said second rotor huband arranged in a Halbach array; a second plurality of airfoils securedto said second rotor hub; and a second magnetic bearing secured to saidfairing, distal ends of said second plurality of airfoils being operablycoupled with said second magnetic bearing.
 16. The aircraft of claim 15,wherein said fairing comprises first and second wings extending outwardfrom opposite sides of said fuselage.
 17. The aircraft of claim 13wherein said first rotor hub comprises: a metal ring; and a plurality ofcarbon fiber bands disposed within said ring.
 18. The aircraft of claim15, further comprising: a third drive coil adjacent said first stator; afourth drive coil adjacent said second stator; a first alternatoroperably connected to said first drive coil and said second drive coil;and a second alternator operably connected to said third drive coil andsaid fourth drive coil.
 19. An aircraft, comprising: a fuselage; astator secured to said fuselage; a suspension coil secured to saidstator; a drive coil secured to said stator; a rotor hub operablycoupled with said stator; a plurality of permanent magnets secured tosaid rotor hub, said plurality of permanent magnets arranged to providea series of alternating, opposite magnetic poles; and a plurality ofairfoils secured to said rotor hub.
 20. The aircraft of claim 19,further comprising first and second wings non-rotatably secured to saidfuselage.
 21. The aircraft of claim 19 wherein said drive coil comprisesfirst and second drive coils, and further comprising: a first alternatoroperably connected to said first drive coil; and a second alternatoroperably connected to said second drive coil.
 22. A helicopter,comprising: a fuselage; a main rotor operably connected to saidfuselage; and a tail section extending from said fuselage, said tailsection comprising a stator and a tail rotor, said stator magneticallylevitating said tail rotor.
 23. The helicopter of claim 22, wherein saidstator comprises a suspension coil and a drive coil to magneticallylevitate and rotate said rotor.
 24. The helicopter of claim 22, whereinsaid main rotor rotates about a first axis and said tail rotor rotatesabout a second axis that is substantially perpendicular to said firstaxis.
 25. The helicopter of claim 22, wherein said tail rotor is notmechanically coupled to a drive shaft.
 26. The helicopter of claim 22wherein said tail rotor is not mechanically coupled to a gear.
 27. Anaircraft comprising: a fuselage; an engine secured to said fuselage forproviding thrust; and a lift fan secured to said fuselage, said lift fancomprising a stator and a rotor, said stator magnetically levitatingsaid rotor.
 28. The aircraft of claim 27, wherein said stator comprisesa suspension coil and a drive coil to magnetically levitate said rotorand to rotate said rotor.
 29. The aircraft of claim 27, wherein saidengine is a turbine engine in which said turbine rotates about a firstaxis and wherein said rotor rotates about a second axis that issubstantially perpendicular to said first axis.
 30. The aircraft ofclaim 27, wherein said rotor is not mechanically coupled to a driveshaft.
 31. The aircraft of claim 27, wherein said rotor is notmechanically coupled to a gear.